Dye diffusion in polymer films subjected to supercritical CO2:: Confocal Raman microscopy and modelling

Poly(ethylene terephthalate) films impregnated with Disperse Red 1 from a supercritical CO2 solution were studied using confocal Raman microscopy. Depth profiles of films dyed for different periods of time were measured using the oil immersion approach and concentration-depth plots of the relative dye concentration were generated. A one-dimensional Fickian diffusion model was used to evaluate the diffusion coefficient of the dye from the Raman microscopy data using a non-linear least squares regression. The calculated diffusion coefficient at 200 bar and 80 degrees C was 6.75 +/- 1.01 x 10(-1)4 m(2) center dot s(-1).